Zero intermediate frequency noise blanker

Abstract

An essentially zero intermediate frequency receiver (100) for recovering an information signal from a received signal (110), which includes means for blanking noise signals which may otherwise deteriorate performance, comprises a receiver (10) for recovering the information signal and a noise blanker (28). The receiver (28) comprises at least one conversion mixer (32B) for operating on the received signal (110) to provide an essentially baseband signal (125B), at least one delay filter (40B) coupled to the conversion mixer (32B) for producing a delayed essentially baseband signal, and at least one blanker switch (S1-S4) for operating on the delayed essentially baseband signal to temporarily prevent recovery of the information signal in response to a control signal (58). To provide the control signal (58), the noise blanker (28) is coupled to the receiver (10) for operating on either the essentially baseband signal (125B) or the received signal (110) as a noise blanker input signal.

What is claimed is: 
     
       1. An essentially zero intermediate frequency receiver for recovering an information signal from a received signal said receiver comprising: receiver means for recovering said information signal comprising: a first conversion means for operating on said received signal to provide an essentially baseband inphase signal;   a second conversion means for operating on said received signal to provide an essentially baseband quadrature signal;   a first delay means coupled to said first conversion means for producing a delayed essentially baseband inphase signal;   a second delay means coupled to said second conversion means for producing a delayed essentially baseband quadrature signal;   at least one blanker switch means for operating on said delayed essentially baseband signals to temporarily prevent recovery of said information signal in response to a switch control signal;     means for providing a gain control signal; and   noise blanking means for blanking noise signals which may otherwise deteriorate performance, said noise blanking means coupled to said receiver means for operating on either at least one of said essentially baseband signals or said received signal as a noise blanker input signal to provide said switch control signal;   said noise blanking means comprising; input filtering means for filtering said noise blanker input signal to provide a filtered signal;   amplifier means for amplifying said filtered signal, in response to said gain control signal, to provide an amplified signal; and   means for generating said switch control signal from said amplified signal.     
     
     
       2. The receiver of claim 1 wherein said delay means comprises an R-C lowpass filter. 
     
     
       3. The receiver of claim 1 wherein said conversion means is a pair of mixers connected in parallel. 
     
     
       4. The receiver of claim 1 wherein said input filtering means comprises at least one bandpass filter for filtering said received signal to provide said filtered signal. 
     
     
       5. The receiver of claim 1 wherein said input filtering means comprises first lowpass filtering means for filtering said at least one of said essentially baseband signals to provide said filtered signal.   
     
     
       6. The receiver of claim 5 wherein said first lowpass filtering means filters said essentially baseband inphase signal to provide said filtered signal. 
     
     
       7. The receiver of claim 5 wherein said means for generating said control signal further comprises: second lowpass filtering means for receiving said amplified signal and providing a filtered output signal;   pulse detector means for operating on said filtered output signal to provide an output pulse whenever the noise contents of said filtered signal exceeds a predetermined threshold; and   pulse shaper means for receiving said output pulse and for providing a desired output pulse.   
     
     
       8. An essentially zero intermediate frequency receiver for recovering an information signal from a received signal said receiver comprising: means for splitting said received signal into a pair of input signals;   receiver means for recovering said information signal comprising: at least one conversion means for operating on each one of said pair of input signals to provide a pair of essentially baseband signals in phase quadrature;   at least one lowpass delay means coupled to each one of said conversion means for producing a pair of delayed essentially baseband signals in phase quadrature; and   at least one blanker switch means for operating on said pair of delayed essentially baseband signals to temporarily prevent recovery of said information signal in response to a control signal;     means for providing an automatic gain control (AGC) signal for controlling the sensitivity of a noise blanking means; and   said noise blanking means for blanking noise signals which may otherwise deteriorate performance, said noise blanking means coupled to an output of at least one of said conversion means to provide a noise blanker input signal for operating on at least one of said essentially baseband signals to provide said control signal;   said noise blanking means comprising: input filtering means for filtering at least one of said essentially baseband signals to provide a filtered signal;   amplifier means for amplifying said filtered signal, in response to said gain control signal, to provide an amplified signal; and   means for generating said switch control signal from said amplified signal.     
     
     
       9. The receiver of claim 8 wherein said input filtering means is a first lowpass filter for setting the bandwidth of said noise blanking means to determine the amount of frequency spectrum that said noise blanking means will monitor for noise.   
     
     
       10. The receiver of claim 9 wherein said control signal generating means further comprises: second lowpass filter for receiving said amplified signal and providing a filtered output signal;   pulse detector means for operating on said filtered output signal to provide an output pulse whenever the noise contents of said filtered signal exceeds a predetermined threshold; and   pulse shaper means for receiving said output pulse and for providing a desired output pulse.   
     
     
       11. The receiver of claim 10 further comprising: AGC detecting means, coupled to an output of said second lowpass filter for providing said AGC signal in a feedback loop comprising said second lowpass filter, said AGC detecting means, and said amplifier means.   
     
     
       12. An essentially zero intermediate frequency receiver for recovering an information signal from a received signal, said receiver comprising: means for splitting said received signal into first, second, and third input signals;   receiver means for recovering said information signal comprising: at least one conversion means for operating on each one of said first and second input signals to provide a pair of essentially baseband signals in phase quadrature;   at least one lowpass delay means coupled to each one of said conversion means for producing a pair of delayed essentially baseband signals in phase quadrature; and   at least one blanker switch means for operating on said pair of delayed essentially baseband signals to temporarily prevent recovery of said information signal in response to a control signal; and     means for providing an automatic gain control (AGC) signal for controlling the sensitivity of a noise blanking means; and   said noise blanking means coupled to an input of said conversion means for operating on said third input signal to provide said control signal;   said noise blanking means comprising: input filtering means for filtering said third input signal to provide a filtered signal;   amplifier means for amplifying said filtered signal, in response to said AGC signal, to provide an amplified signal; and   means for generating said switch control signal from said amplified signal.     
     
     
       13. The receiver of claim 12 wherein said input filtering means is a tuned bandpass filter tuned to a fixed frequency spectrum where noise is expected.   
     
     
       14. The receiver of claim 13 wherein said control signal generating means further comprises: tuned bandpass filtering means for receiving said amplified signal and providing a filtered output signal;   pulse detector means for operating on said filtered output signal to provide an output pulse whenever the noise contents of said filtered signal exceeds a predetermined threshold; and   pulse shaper means for receiving said output pulse and for providing a desired output pulse.   
     
     
       15. The receiver of claim 14 wherein said means for providing an automatic gain control (AGC) signal comprises a received signal strength indicator for indicating the strength of said received signal to provide said AGC signal.